Technical Abstract:
Understanding how sward structure affects grazing behavior of ruminants requires knowledge of sward-animal interactions at the bite level. Therefore, the effect of sward structure of four grass species on bite mass of grazing dairy cows was evaluated. Holstein cows were offered micro-swards (79 cm x 47 cm x 11.5 cm) of one of four grass species [reed canarygrass (RCG), quackgrass (QG,), orchardgrass (OG), and meadow fescue (MF)] in short-term foraging tests in each of two years (2006, 2007). Cows were allowed to take 50 bites in each test. Bite mass was calculated by dividing the adjusted micro-sward weight change by the number of bites. Sward height, bulk density, and distribution of dry matter in the canopy were measured pre- and postgrazing. Mean fresh and dry matter (DM) bite masses were not affected by grass species. Fresh and DM bite masses were greater during 2006. Herbage mass and sward surface height were greatest for RCG in both years. Bulk density was not affected by treatment (species) in 2006, but was greatest for MF and RCG in 2007. Despite differences in sward structure within each year, bite mass in cattle grazing these four grasses was not affected.